mineral
Mica (Lepidolite or Muscovite)
Phyllosilicate mineral (KAl2(AlSi3O10)(OH)2 for Muscovite)
Hardness: 2.5-4 (Mohs); Color: Silvery-white, gray, or lilac; Luster: Pearly to vitreous; Crystal Structure: Monoclinic; Cleavage: Perfect basal (peels in sheets); Specific Gravity: 2.82
- Hardness
- 2
- Color
- Silvery-white, gray, or lilac
- Luster
- Pearly to vitreous
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Physical properties
Hardness: 2.5-4 (Mohs); Color: Silvery-white, gray, or lilac; Luster: Pearly to vitreous; Crystal Structure: Monoclinic; Cleavage: Perfect basal (peels in sheets); Specific Gravity: 2.82
Formation & geological history
Formed in igneous pegmatites or metamorphic rocks like schist and gneiss through hydrothermal processes or regional metamorphism. Often found in continental crust environments.
Uses & applications
Used as an electrical insulator, in cosmetics (sparkle in makeup), in joint compound for drywall, and as a heat-resistant window in stoves (Isinglass).
Geological facts
Mica is unique because it can be split into extremely thin, flexible, transparent sheets. Large sheets of mica were used for windows in Russia before glass became common.
Field identification & locations
Identify in the field by its 'books' of thin, flaky layers that can be peeled with a fingernail. Commonly found in granite-rich areas and mountain belts.
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Other mineral specimens
Sandstone (with potential mineral staining/concretions)
Arenite (SiO2 based)
sedimentary
Schist
Schist
Metamorphic
Epidote
Epidote | Ca2(Al2,Fe3+)(SiO4)(Si2O7)O(OH)
metamorphic
Gypsum (variety Selenite or Alabaster)
Calcium sulfate dihydrate (CaSO4·2H2O)
Mineral
Nephrite Jade
Nephrite
Mineral/Rock
Banded Gneiss (River Rock/Pebble)
Gneiss (specifically a banded variety often found as a river rock)
Metamorphic Rock